You spend weeks studying
for an important test.
On the big day, you wait nervously
as your teacher hands it out.
You’re working your way through,
when you’re asked to define ‘ataraxia.’
You know you’ve seen it before,
but your mind goes blank.
What just happened?

The answer lies in
the complex relationship
between stress and memory.
There are many types
and degrees of stress
and different kinds of memory,
but we’re going to focus on
how short-term stress
impacts your memory for facts.

To start, it helps to understand
how this kind of memory works.
Facts you read, hear, or study
become memories through
a process with three main steps.
First comes acquisition:
the moment you encounter
a new piece of information.
Each sensory experience activates
a unique set of brain areas.

In order to become lasting memories,
these sensory experiences
have to be consolidated
by the hippocampus,
influenced by the amygdala,
which emphasizes experiences
associated with strong emotions.
The hippocampus then encodes memories,
probably by strengthening
the synaptic connections
stimulated during
the original sensory experience.

Once a memory has been encoded,
it can be remembered,
or retrieved, later.
Memories are stored all over the brain,
and it’s likely the prefrontal cortex
that signals for their retrieval.

So how does stress
affect each of these stages?
In the first two stages,
moderate stress can actually
help experiences enter your memory.
Your brain responds to stressful stimuli
by releasing hormones
known as corticosteroids,
which activate a process
of threat-detection
and threat-response in the amygdala.
The amygdala prompts your hippocampus
to consolidate the stress-inducing
experience into a memory.
Meanwhile, the flood
of corticosteroids from stress
stimulates your hippocampus,
also prompting memory consolidation.

But even though some stress
can be helpful,
extreme and chronic stress
can have the opposite effect.
Researchers have tested this by injecting
rats directly with stress hormones.
As they gradually increased
the dose of corticosteroids,
the rats’ performance on
memory tests increased at first,
but dropped off at higher doses.
In humans, we see a similar
positive effect with moderate stress.
But that only appears when
the stress is related to the memory task—
so while time pressure might
help you memorize a list,
having a friend scare you will not.
And the weeks, months, or even years
of sustained corticosteroids
that result from chronic stress
can damage the hippocampus
and decrease your ability
to form new memories.

It would be nice if some stress
also helped us remember facts,
but unfortunately, the opposite is true.
The act of remembering relies
on the prefrontal cortex,
which governs thought,
attention, and reasoning.
When corticosteroids
stimulate the amygdala,
the amygdala inhibits,
or lessens the activity of,
the prefrontal cortex.
The reason for this inhibition
is so the fight/flight/freeze response
can overrule slower, more reasoned
thought in a dangerous situation.
But that can also have
the unfortunate effect
of making your mind
go blank during a test.
And then the act of trying to remember
can itself be a stressor,
leading to a vicious cycle
of more corticosteroid release
and an even smaller chance of remembering.

So what can you do to turn stress
to your advantage
and stay calm and collected
when it matters the most?
First, if you know a stressful
situation like a test is coming,
try preparing in conditions similar
to the stressful environment.
Novelty can be a stressor.
Completing practice questions
under time pressure,
or seated at a desk
rather than on a couch,
can make your stress response
to these circumstances
less sensitive during the test itself.

Exercise is another useful tool.
Increasing your heart
and breathing rate
is linked to chemical changes
in your brain
that help reduce anxiety
and increase your sense of well-being.
Regular exercise is also widely
thought to improve sleeping patterns,
which comes in handy
the night before a test.